and may reach a size of 20 mm., their extreme width 

 being 11 mm. The (hjrsal face of the body is moderately 

 convex, and its surface is granulated. The body can be con- 

 veniently divided into four regions — 1, the head segment 

 or cephalou ; 2, the mesosome or thorax, consisting of 

 seven segments; 3, the metasome or abdomen, consisting 

 of five distinct abdominal segments, together with a 

 terminal segment, which is, 4, the telson. 



The cephalon is sunk into a depression formed by 

 the forward growth of the epimeral portions of the first 

 thoracic segment. It is evenly convex in front ; the 

 posterior border is depressed, the edge being marked by 

 a ridge. The dorsal surface is slightly curved trans- 

 versely. A pair of large compound sessile eyes are 

 situated laterally, each having a slight reniform appear- 

 ance from a dorsal view. On the anterior face, which is 

 almost vertical, the minute pair of first antennae are 

 situated, one on each side the median line. To the 

 Dutside of these are the large and robust second antennae. 

 When moving, the animal holds the large antennae in a 

 forward position, and constantly tests the nature of the 

 surface over which it is proceeding with the very sensitive 

 fiagella, appearing to trust for guidance more by this 

 means than by means of its sight. When at rest, they are 

 folded back along the sides of the mesosome. 



( )u the ventral side of the head the mouth-parts form 

 a prominent projection. The mouth is bounded in front 

 by a large transversely-hinged labrum. The sides ar(^ 

 composed of the powerful mandibles and two pairs of 

 maxillae. Tlie posterior border is formed by the two 

 maxillipedes, which are imperfectly fused together, 

 forming an apparent lower lip; there is, however, internal 

 to these, a lingua-like bilobed chitinous plate, deeply 

 incised in the middle and having a small median plate; 



